Page authors: Don Knoke, David Giblin
Sonchus arvensis
field sow-thistle, perennial sow-thistle
WTU images
WTU specimens
Other herbaria

Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across most of North America to the Atlantic Coast.

Habitat: Balds, prairies, forest edge, stream banks, roadsides, fields, and other disturbed open areas generally at low elevations, often where moist.

Flowers: July-October

Origin: Introduced from Europe

Conservation Status: Not of concern

Description:
General:

Perennial with long vertical roots and creeping horizontal roots, glabrous below the inflorescence, 4-20 cm. tall.

Leaves:

Leaves prickly margined, the lower and middle ones pinnately lobed or pinnatifid, 6-40 cm. long and 2-15 cm. wide, becoming less lobed, smaller and widely spaced upward.

Flowers:

Heads several in an open, somewhat flat-topped inflorescence, 3-5 cm. wide in flower; fruiting involucre 15-22 mm. high; involucres and peduncles covered with glad-tipped hairs in one variety, glabrous in the other.

Fruits:

Achenes 2.5-3.5 mm. long, with 5 or more prominent ridges on each face.

Identification Notes:

This is the only perennial species of Sonchus found here, and it is generally a larger plant with much larger flowering heads than the annual species.

Accepted Name:
Sonchus arvensis L.
Publication: Sp. Pl. 2: 793. 1753.

Synonyms & Misapplications:
(none provided)
Infraspecies:
ssp. arvensis – corn sow-thistle, field sow-thistle, perennial sow-thistle    Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across most of North America to the Atlantic Coast.
ssp. uliginosus – field sow-thistle, marsh sow-thistle, wet ground sow-thistle    Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across most of North America to the Atlantic Coast.
Additional Resources:

PNW Herbaria: Specimen records of Sonchus arvensis in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Sonchus arvensis checklist entry.

E-Flora BC: Sonchus arvensis atlas page.

CalPhotos: Sonchus arvensis photos.

USDA Plants: Sonchus arvensis information.

29 photographs:
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